I got successful install of esp8266/Arduino 0.4.5 on a Windows7 32bit machine today.
I have the same missing file error as @mikekgr on a Ubuntu linux 32bit machine today.
This bug is keeping new linux 32bit users of esp8266/Arduino from being able to install.
edit: There is a esptool-0.4.5-linux32.tar.gz file sitting on my local hard drive in the
.arduino15/staging/packages folder on my machine. (Select 'Show Hidden Files' from the Home directory.)
The installer is looking online in the github website for it... so close yet so far